Proton formation in oxides

Doping by aliovalent cations is indispensable for the appearance of protonic conduction in these oxides. It seems that electron holes and oxide ion vacancies formed by doping might play an important role in the formation of protons. For example, substitution of Yb for Ce in SrCeOg may provide oxygen vacancies Vq as a means of charge compensation  

The oxygen vacancies may be in equilibrium with electron holes as shown in Eqn (8.7) below. Possible equilibrium reactions and schematic defect chemistry for proton formation in SrCej, jYbjt03 are shown in Fig. 8.9. 

Studies on electrical conductivity as a function of dopant content, or partial pressures of water vapour and oxygen have shown that the 

In order to clarify the process of dissolution of water vapour (or hydrogen) to generate protons in SrCeOg-based oxides at high temperature, the evolution and the absorption of water vapour and/or oxygen were studied by changing the temperature or partial pressure in a flow of wet or dry gases °. 

The hydrogen concentration in SrCeg. 9sYbg, gjOg-a which had been equilibrated with a certain water vapour pressure was measured by the SIMS method and thermal desorption . Fig. 8.10 shows the amount of evolved water vapour per mole of oxide measured by thermal desorption during heating from 600 °C. 

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High temperature proton conductors 8.6 Proton formation in oxides... 

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